Attachment for flexible rotary disks



Nov. 28, 1950 s. M. KENERSON ATTACHMENT FOR FLEXIBLE ROTARY DISKS Filed Feb. 7, 1949 INVENTOR Jrmvzzrfifiwmsom BY QM 144 ATTORNEYS Patented Nov. 28, 1950 UNITED STATES PATENT OFFICE ATTACHMENT FOR FLEXIBLE ROTARY DISKS Stanley M. Kenerson, Springfield, Mass.

Application February '7, 1949, Serial No. 75,037

. 1 Claim.

This invention relates to an improved attachment for flexible discs of the rotary type used for sanding and polishing and the like with standard portable electric drills.

One object of this invention is to provide an improved construction which will permit the attachment of an abrasive or sanding sheet to the disc without wrinkling or tucking of the same.

Another object is to provide an arrangement whereby the flexing of a disc is confined to the outer edges thereof to prevent the creeping of an abrasive sheet at the lines of attachment and the consequent rapid deterioration of said sheet in use.

These and other objects and advantages will be seen from the following description of a preferred form of the invention as shown by the accompanying drawings, in which:

Fig. 1 is a sectional view of a disc attachment showing the assembled construction;

Fig. 2 is a view on line 2-2 of Fig. 1;

Fig. 3 is a fragmentary plan view showing the central recessed portion of a flexible disc;

Fig. 4 is a plan View of an abrasive sheet prepared for assembly in the unit as shown by Fig. 1; and

Fig. 5 is a fragmentary plan View of a spindle head plate holding the abrasive sheet of Fig. 4 in assembled position on the face of the disc.

Referring to Fig. 1, a spindle l is adapted at its inner end for attachment to a rotary power driving means such as a standard portable electric drill (not shown). A drill of this type is well known as are the various types of drill chucks in which the spindle may be held for use.

At the outer end portion of the spindle I an enlarged threaded portion 2 is provided for the attachment of the disc assembly as will be described. At the tip end of the spindle a head plate 3 is fixed as by brazing or by any other suitable type of rigid mounting so as to be securely attached thereto for rotation with the spindle. Preferably the plate is metallic and on its flat outer surface a layer of resilient nonabrasive material may be bonded as a layer 4 of rubber.

On the spindle l is mounted a circular disc 5 of rubber or other suitable flexible material. The disc 5, as shown, is provided with a flat outer surface 6 on the outer portions of the disc and a centrally located recessed portion 1 to accommodate the head plate 3 of the spindle.

The recess 1 as shown by Fig. 3 is square in outline and has a relatively deep inner section at with straight walls and an outer section with .2 beveled walls 9. The beveled edges 9 are dimensioned to receive the edge of head plate 3 against the same to recess the plate below the surface 6 of the disc. The plate 3 is thus recessed into the disc and the face of its rubber layer 4 substantially flush with the surface 6.

The opposite side of disc 5 is formed with a flanged hub It! defining a centrally disposed area in excess of the central area outlined by the recess on the face of the disc (Fig. 2). A metallic cap or hub cap H is mounted on the spindle to overlie the flanged hub in superimposed position. A nut I2 is threaded on the portion 2 of the spindle to hold the assembly of disc and cap tightly clamped between the plate and nut.

In Fig. 4 a circular sheet it faced with an abrasive is shown for mounting in the attachment assembly of Fig. 1. The central portion thereof has been arranged with flaps to be held in the recess by the head plate of the spindle as illustrated in Fig. 5. An opening I4 is cut in the sheet for passage of the spindle shank. Radial slits l5 extend from the corners of the opening to meet the ends of hinge lines l6 scored to coincide with the edges of the beveled portions 9 of the disc recess. Flaps ll, thus formed, are adapted for bending at said edges of the beveled recess walls to be held therein in clamped position with the sheet 13 lying flat on the surface of the disc (Figs. 1 and 5).

The clamping of the abrasive sheet against the beveled walls 9 is confined to the flaps I! which in assembled position are separated as at It (Fig. 5). Thus the abrasive sheet is clamped to provide a flat relationship of the working surface at the edges of the recess whereby no wrinkles or tucks result from its tightening on the disc. The layer of rubber 4 provides a safeguard to prevent marring of the work surface due to accidental contact.

The plate 3 in clamping flaps I! as described holds each of said flaps on a single grip line of contact. In use the reinforcing cup, hub cap II, as disclosed bears at its outer circular lip portion against the disc to prevent the flexing of the central recessed portions. Flexing of the disc is thus confined to the outer portions as illustrated by the dotted line position of Fig. 1. The central portion of the disc adjacent the recess remains in normal flat position and creeping of the abrasive sheet is prevented. Plate 3 would otherwise tend to bite flaps \IT at different line contacts under the pull of a disc flexed immediately adjacent the recess. The clamping of sheet 13 as disclosed thus prevents wrini) In a flexible disc attachment assembly the combination of a circular disc of flexible material having a flat face adapted to receive an abrasive sheet against the same and a square recess centrally disposed in said face with the 10 outer side portions of the recess beveled, said-disc in its central body portion being thickened around said recess to provide a relatively rigid central hub portion and an outer peripheral flexible flange portion, a spindle shank receivingop'eningdfi in said central body communicating with the bottom of said recess, a hub cap of rigidmaterial having a central opening coinciding with said spindle shank receiving opening and extending peripherally over the thickened hub portiontqeo overlie the disc at the back of the inner margin o the-,,, eXi flan d. p rt on .of a d i c, a in,- dle" with a circular threaded. shank extending throughfsaid openings and provided with arsquare heajd rplate at theend thereof 13 mg in' thefrece ss 25 with its edges bearing against the beveled sides of the recess, said head plate having an outer facing of resilient non-abrasive material to lie inset in said recess below an abrasive sheet surface on the disc, and a clamp nut threaded on said spindle shank to bear against said hub cap and draw said head plate tightly in said recess.

STANLEY M. KENERSON.

REFERENCES CITED Ihe following referehces are ofi'ecord in the file of this patent:

H UNITED STATES PATENTS Number 351? 'Name Date 1,176,001 Stewart Mar. 21, 1916 1 5 187,853 Koreneir June 8, 1926 1,693,163 Schacht Nov. 27, 1928 l,- 749-, 709-- Loveland Mar. 4, 1930 zeta e03 Baur Oct. 3, 1944 FOREIGNPATENTS Number ooustr'y 9 Date Germany Mar. ;22,-' 1931 

